Therapeutic horseback riding (THR) is frequently sought out as an alternative treatment to address the behavioral disturbances that often impair the quality of daily life for individuals with an autism spectrum disorder (ASD); however, there are only a few published evidence-based THR studies to guide clinicians and consumers. This study aims to expand on our pilot study findings of significant improvements in self-regulation, communication, and motor skills for ASD participants involved in 10-weeks of therapeutic horseback riding compared to a 10-week waitlist control group. This proposed study will attempt to replicate these pilot findings as well as the social motivation findings from a recent THR study by examining a larger sample and using a randomized control design. Furthermore, it will test whether the human-animal interaction is necessary for the significant changes observed in the pilot study. This question will be examined by comparing ASD participants' involvement in 10 hours of weekly therapeutic horseback riding (n = 40) to a barn activity control group (n = 40) that targets the same therapeutic goals and controls for time and attention effects, but has no human-animal interaction. Pre-and post intervention evaluations will assess participants' self-regulation, communication, socialization, and motor functioning. A secondary aim of the study is to determine if improvements made as a result of involvement in 10-weeks of therapeutic horseback riding persist approximately six months beyond the THR intervention. The strengths of this research project include the use of a randomized controlled design, an activity-based control group, a specific THR intervention curriculum developed from our pilot project, outcome evaluators blinded to participants' intervention condition, parent and teacher outcome ratings, and previously-developed collaboration with a long-standing (29 years) intervention site. This riding center site is certified as a Premiere center by the NARHA, a national accrediting agency that adheres to the highest standards in the industry for human and animal safety and ethical standards for all living beings involved in the treatment process. PUBLIC HEALTH RELEVANCE: There are a large number of families of children with an ASD that seek this intervention, even though there is little evidence base. Determining if and how the human-animal interaction via THR is helpful to individuals with an ASD has far-reaching implications for the quality of life in this ASD population and their caregivers. THR is less invasive than the use of medications to treat symptoms such as irritability and hyperactivity, critical areas that impact the child's ability to function successfully in home and school environments.